If you have an older Travel Trailer or Fifth Wheel you should know that according to Federal law, DoT cylinders may only be used for 12 years after their manufacture date. After that, the cylinders must be “re-certified” which provides another five years of use. The cylinders can be re-certified every five years thereafter.
Check the date stamped on your cylinders… don’t rely on your rig’s model year even if the cylinders are original. It’s quite possible they are a year or more older than your rig. Ours were.
Propane venders are legally required to look at the date stamped on the cylinder before filling it. Some actually do look. We’ve been reminded a few times that our cylinders were about to expire.
Re-certification is usually done by the large bulk propane suppliers but we found one of our local RV repair shops was certified to do the job and they do it for free! Call around to see who may do it in your area.